Keyboard for musical instruments



May 17, 1949.

cs. w. DEMUTH KEYBOARD FOR MUSICAL INSTRUMENTS 2 Sheets-Sheet 1 Filed Sept. 28, 1944 III w I N E w flfi I}- llll: I 1 m w u HA ww m @ww wm I IT n yrrae/vn May 17, 1949. e. w. DEMUTH KEYBOARD FOR MUSICAL INSTRUMENTS 2 Sheets-Sheet 2 Filed Sept. 28, 1944 INVENTOR. fi/mw W. flaw/TH BY FTTOE/YE/ Patented May 17, 1949 KEYBOARD FDR MUSICAL INSTRUMENTS Galan W. Demuth, Moorestown, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application September 28, 1944, Serial No. 556,122

3 Claims. 1

This invention relates to musical instruments which have manual keyboards (for example, pianos and organs), and has particular reference to an improved keyboard for such instruments.

The practical production and rapid adjustment of keyboards of conventional Wooden construction necessitates the employment of a limited class of qualified labor for a number of precise operations, such as key leveling, regulation of touch, and key dip.

A prime object of the invention is to provide an improved keyboard adapted for quantity production at low cost by modern factory processes which may be carried out by relatively unskilled labor employing efficient tools and fixtures, jigs and the like.

Another object of the invention is to provide an improved keyboard with a novel and highly eiiective suspension arrangement of the keys.

It is another object of the invention to provide an improved keyboard which shall, in general, be free from the problems inherent in wooden construction.

It is a further object of the invention to provide an improved keyboard which shall be free from sticking, rapid in action, permanent in adjustment, easily constructed of interchangeable parts and pleasing in touch.

Another object of the invention is to provide a keyboard having improved means for the easy regulation of the action of the keyboard, including key level and touch.

In carrying the invention into effect, many of the parts of the keyboard are made interchangeable, and may be constructed of sheet metal. The assembled keyboard consists of a plurality of movable key arms of fabricated sheet metal, each having a non-metallic key head secured to the forward end of the key arm. These arms are suspended from a rigid, transverse key frame member, which may also be of metal, by means of individual flat springs which are limber in the normal direction of motion of the keys, that is, vertically, but which resist lateral displacement, so that adjacent keys are prevented from touching or dragging against each other. These springs also supply restoring forces which maintain the keys at their upper point of rest and determine the touch. Means are also provided which introduce a slight resistance or damping to the key in its vertical motion, and the touch quality desired by musicians accustomed to conventional pianos and organs is thus further enhanced.

The invention may be better understood from a consideration of the following description of three embodiments thereof, when read in conjunction with the accompanying drawing in which:

Figure l is a fragmentary plan view of a keyboard constructed in accordance with the inven tion, and showing one octave of the keyboard,

Figure 2 is a vertical sectional View taken along the line II-II of Figure 1,

Figure 3 is a plan view in simplified form of an alternative spring construction for the suspension of the key arms,

Figure 4 is a plan View of another embodiment of the invention and showing, for the sake of greater clarity, an assembly of only one white and one black key, and

Figure 5 is a view in front elevation of the embodiment of Figure 4, with a portion of the key frame broken away to reveal elements under the key heads.

In Figs. 1 and 2 are shown a plurality of movable key arms ill fabricated of sheet metal, such as steel or aluminum, and preferably, but not essentially, channel-shaped. Key heads I2, which may be of wood or plastic material, are secured to the key arms at their forward ends as by means of the screws I l. The key heads may extend beyond the forward ends of the key arms. The keys thus constituted are arranged side by side as in a conventional keyboard (see Fig. 1).

A rigid, stationary frame member [6, also of sheet metal, extends above and transversely of the keys so arranged and each key is suspended from this member by means of a fiat spring I8. Each spring is secured at one of its ends to the frame member it as by means of a clamping plate 9E and rivets 25!. The other end of each spring is removably secured to a bracket M mounted on the key arm as by means of clamps 92 and screws 22. Each key, including the key arm id and the key head [2 mounted upon it, is completely free of mechanical attachment except where suspended from the frame by the spring 13. The frame member may, therefore, be regarded in a sense as the fulcrum about which the keys move vertically. The spring in the embodiment shown was I a" wide, .020" thick and nearly 3 inches long, and it will be seen that the effective working portion of the spring is the short, unclamped portion extending between the clamps and 92. The clamps thus prevent indeterminate flexing of the spring. It is desirable that the limited working portion of the sprin be short, since otherwise each key assembly may easily be twisted.

The spring has substantial compliance in a vertical direction, but negligible horizontal compliance, and in the assembly of the keyboard the keys are so applied as to permit each key arm to move up and down freely, but not to be displaced sideways to any objectionable degree. In general, therefore, adjacent keys do not touch or drag against each other. As before mentioned, the spring serves also to supply the restoring force required to maintain the key at its upper point of rest, and partially determines the touch of the keyboard.

It will be seen that each flat spring I8 is not secured directly to the key arm it but to the offset bracket 24. This is done in order to have the spring in substantially the same horizontal plane as the top of the key head B2. In the absence of such an arrangement, it was found that in normal operation of the keys, and particularly of the white or natural keys which have longer key arms, random lateral forces against the sides of the keys caused a twisting of the keys. When the keys are assembled in the completed keyboard in side-by-side relation, this twisting may be noticeable as a lateral displacement of the individual .keys, due to the flexible tilting or leaning of thetop face of the key head from side to side, and thus towards adjacent keys. The introduction of the bracket 24 raised the spring to the level of the top of the key head, and eliminated this undesirable feature. For greater rigidity the bracket has the table-like shape which may be seen in Fig. 2.

Beneath the forward ends of the key heads and extending transversely of them is another channel-shaped member 26, also of fabricated sheet metal, arranged with the open side downwards to form a table-like structure, the top of which is covered with felt 28. While any material capable of deadening impact sound, for example, oiled leather, is suitable in this respect, I prefer to use the kind of woven felt commonly employed for this purpose in pianos. When any key is depressed, the bottom of the key head comes in contact with the felt and the operation is then substantially silent.

Beneath the rearward ends of the key arms is another and similarly arranged transverse, channel-shaped frame member 30 covered with felt pads 32 and 34 at the top and forward side, re-

spectively. A formed spring 36 secured to each movable key arm, as by means of the screw 38, slides against the stationary felt pad 3d, the pres- .sure of the sliding spring being such that a uni form and appreciable friction results. The friction thus created introduces a slight resistance or damping to the downward movement of the key when depressed, and to its upward movement when released, thus eliminating the vibration or rebound which might result when the key is released suddenly in the depressed position. This damping action substantially improves the touch of the instrument, resulting in What may be described as a soft touchnot snappy or hard, as would otherwise result from springactuated keys. The felt pads 28, 32 and 3 are cemented or otherwise fastened to the surfaces which they cover.

An .aperture M] in each key arm at its rearward end is adapted to receive a threaded key stop 42. This has a flat head 44, which rests against the felt pad 32, and mounted on the stop is a threaded lock nut 48, and also a square nut 84 which is within the channel and therefore cannot'turn. Adjustment of the position of the key stop below the key arm determines the upper or rest position of each key, and the lock nut secures the stop in that position.

Depression of any key causes vertical movement of the key arm, and in the case of instruments like the piano or some non-electrical organs, this movement initiates mechanical operations which, in turn, produce musical sounds. The invention is, however, here illustrated in connection with an electrical musical instrument, and the key arm therefore carries at its rearward end a bumper 38 adapted to cooperate with contact blades to and 52 which form a part of an electrical circuit (not shown). However, the mechanical construction of the keyboard herein disclosed may be incorporated in the design of conventional non-electrical musical instruments, as will be apparent to those familiar with such instruments.

In the embodiment described, each key arm is suspended by an individual flat spring 13 and there will thus be as many springs as there are keys. In the embodiment shown in Fig. 3, this plurality of springs is replaced by a single, wide, fiat spring member E i, the continuous side of which is clamped or otherwise secured to the key frame it. The other side is slotted as shown, thereby producing a plurality of individual tongues 58a, iiib, lSc, etc., each corresponding to one of the flat springs it of the previously described embodiment. Each tongue is secured to the bracket 25, mounted on each key arm, and thus each key is individually suspended, while the arrangement provides for greater accuracy and convenience in assembly.

In the embodiment illustrated in Figs. e and 5, the length of the key arm it) is reduced, thereby diminishing the mass, and therefore the inertia of the key arm, and also its cost. It will be seen that in this embodiment the formed damping spring 38 is secured to the forward end of the key arm iii, and engages a felt pad 55 cemented to the side of a channel-shaped member 58, located under the key head I2. This member serves in this respect the same purpose as the similarlyshaped member 3c of the embodiment of Figs. 1 and. 2. When a long or natural key is depressed, it comes in contact with a felt pad at secured to the top of the member 58.

The key frame member 96 is secured to upright supports 62 on either side of the keyboard by screws 5 and which pass through apertures t8 and id in the supports. The rear aperture 658 is a slot. The slot permits tilting of the key frame member in a horizontal plane. It will be seen that this adjustment effects the bending of all suspension springs simultaneously,

and consequently varies the restoring force or pressure of touch for all the keys suspended from the member i5.

An individual adjustment of the level of each key is afforded by a soft steel tongue l2, forming part of a long, slotted angular piece which is spot Welded or otherwise secured to a rigid frame member 75. This frame member extends beneath and transversely of all the arms of the keyboard. The individual key arm assembly "includes a key-stopping bracket M which is welded underneath the key arm, so that when the key arm is in the upper or rest position the bracket or key-stop M is in contact with a felt pad '28,

cemented on the individual adjusting tongue l2. This soft steel tongue has a round aperture formed therein. Adjustment of key level and dip is easily effected during production of the keyboard by inserting a piece of drill rod in the aperture 80 and bending the bracket 72 to the desired height.

A felt pad 96 cemented to the top of the frame member 16 constitutes a lower stop, and determines the dip of the short or sharp keys. In the embodiment described this stop is not adjustable and serves the same purpose as does the Dad 60 for the long keys.

There has thus been described an improved keyboard having a novel suspension and regulating arrangement for the keys, as well as superior touch. The keyboard may be constructed in quantity by labor not highly trained in the trades or crafts associated with the manufacture of musical instruments, because of the use of uniformly interchangeable parts of high accuracy constructed of sheet metal and the like. In similar instruments of the prior art, this is achieved only by individual modification and fitting of the parts in the assembly during initial construction.

I claim as my invention:

1. In a musical instrument having a keyboard, the combination of a plurality of key arms arranged laterally, a stationary key frame member, and a, flat spring secured at one side thereof to said member and slotted at the opposite side thereof whereby to form a plurality of tongues, each of said tongues being rigidly secured to one of said arms whereby each of said arms is suspended from said member.

2. In a musical instrument manually operable by keys, a keyboard comprising a key frame member of sheet metal, a plurality of key arms of sheet metal arranged in lateral relation with each other beneath and normal to the key frame member, spring means having negligible lateral motion connected to the frame and the arms for suspending the arms from the frame, a plurality of key heads corresponding in number to the key arms secured to the arms at their forward ends and extending forwardly beyond said ends, a felt-covered, channel-shaped member of sheet metal extending in a direction normal to the key arms beneath and spaced from the key arms, formed springs secured to each of the arms and engaging part of the felt covering of the lastmentioned member for damping motion of the arms, and adjustable means associated with each of the arms for determining the rest position of each of the arms.

3. In a musical instrument having a keyboard,

I the combination of a plurality of key arms arranged laterally, a stationary key-frame member above said arms and extending transversely thereof normally in a substantially horizontal plane, resilient key-suspension means secured to said member and said arms, and adjustable means for tilting said key frame member at an angle to the horizontal.

GAL-AN W. DEMUTH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 17,320 Driggs May 19, 1857 43,389 Burton July 5, 1861 1,200,336 Foust Oct. 3, 1916 1,319,188 Swallow Oct. 21, 1919 1,663,146 Socin Mar. 20, 1928 2,117,002 Hammond May 10, 1938 2,184,424 Hammond Dec. 26, 1939 2,260,412 Stephens Oct. 28, 1941 

